Yielding pressure welding



Nov. 10, 194?. u ETAL 2,301,173

YIELDING PRESSURE WELDING Filed Feb. 11, 1938 Gad/ave K. .Blum Arfizurlljeiera,

kM g. 4

Patented Nov; 10, 1942 BEST AVAILABL copy I I assignmto The McKay Company, Pa, a corporation. of Pennsylvania Application February 11, 1938, Wm. 190,032 J 1:: ohm (cans-s) This invention relates to yieldingpressure welding and has for its object the provision of amethod and apparatus for making better welds with less current than is possible with ordinary welding.-

A second objectof the invention is to provide a method of welding links of chains, especially chain of high carbon or alloy steels, on a standard automatic chain welding machine with only slight alteration of the machine itself and providing f sbu zh.

men by long practice are able to theclutch more uniform and better welds while increasing the yielding of theabutting ends but also to the bending of the back of the link.

Another object of the invention is to provide a fully automatic chain welding machine which stops the welding current in response to a desired condition including the temperature of the joint being welded and relatively independent of other factors such as time. current or voltage.

An important object of the invention is to provide a method of welding together opposed sur faces by a combination of a butt welding opera- 1 tion. a. flash welding operation and a resistance r welding operation, this combination when applied to a standard chain making. machine for instance providing a remarkably uniform finished chain because the method causes the machine to work with varying time cycles, each weld being given exactly the proper timing irrespective of whether the link is long or short.

In the ordinary manufacture of chains the welds are made by automatic machinery in case of the smaller chains of low carbon content but it is usual to weld the better grades of chain, particularly those of high carbon or alloy steels such as those containing nickel and molybdenum, by manually operated machines wherein the workleverto open the welding circuit at precisely the right time,'within the usual limits of human accuracy. Even with'the very best of workmen however there is a sharplimit to the tempera-' ture that may be employed without "burning" the Joints and yet it has been apparent to us for some time that if we could 'increasematerlally the temperature of the welding we would have a much better joint provided we could prevent the burning of the links which we believed we could avoid by the use of a more properly timed and higher upset than is provided by the standard chain-welding machines now in use. We also felt that the standard machine could be speeded up by the use of higher transformer capacity which would give a quicker heat and it seemed to use this would lend itself nicely to the total elimination of the double step which is common in practically all chain welding ma chines in actualuse whether of manual or automatictvm.

In the past there has been little trouble with the quality of the chain made with-low carbon stock and we have frequently tested such chain links by bending them through an angle of 180' with the weld as an axis. With the better grades of chain now coming more and more into use many seemingly excellent welds will not stand a bending in this manner, even as little as 45 and the characteristic weld cracks are almost invariably present in the better quality steels made prior to this invention but these cracks are strikingly absent when chain is made in the manner hereinafter set forth.

In the chain welding machines well known in the art the blocks carrying the electrodes are loosely mounted in their sockets and the vertical posts rising from the blocks are rigidly held a chosen distance apart by a sturdy brace or strap pivotally secured to the top of each post so as to prevent the posts from spreading apart as they would otherwise do by reason of the necessary looseness of ill: of the blocks in their pivot sockets, this looseness being necessary because of the expansion of the blocks due to the great heat which is unavoidably created in the blocks by the induced currents. A characteristic of the apparatus, which is but one form of carrying out our process. is that the brace or strap is replaced by spring means whereby the posts are yieldingly urged toward each other at their tops and in the preferred embodiment it is the movement of the (a) The better quality of each individual weld; (b) The remarkable increase in uniformity in the gage length of the finished chain due to the fact that the welded links are all of the same length although the formed links were not;

(c) The many-fold increase in the life of the electrodes;

(d) The decrease in amperage as the weld is being made;

(c) The increase of automatic efliciency which makes it easy for a single operator to care for a number of machines and at the same time increasing the over-all life of the machine while increasing the production in pounds per hour, the latter increase running to rather surprising figures in view of the rather well-worked state of the art.

Other advantages are of relatively less importance and will be apparent as the description proceeds, for example, the fin or burr which is made in our process of welding is appreciably less hard than with the standard welding machines with the result that the trimmer lasts longer than in the usual method of chain welding.

Figure l is a plan view of an automatic chain welding machine equipped with one embodiment of our invention.

Figure 2 is a sectional view taken on line 2-2 oi Figure 1 and to which a diagram is added to show the electrical circuits.

The chain welding machine shown in Figure 1 is generally of well known type comprising a table II on which is mounted at the rear the main shaft II which drives the chain advancing devices H by way of shafts l5. and oscillates the welding blocks l6 toward and away from each other by means of the face cams l8 acting on the cam followers I9 carried by the ends of the arms rigidly secured to the welding blocks. Upper and lower swaging hammers are arranged to be driven by a cam 22 located between-the two face cams but to simplify the drawing the upper hammer is broken away to show more clearly the lower hammer 24. At the front right end of the table there is shown the usual trimmer 26 for removing the burr or fin from the links as they come from the welding mechanism. A clutch 30 ard machine the posts 36 are tied together at the top by means of a rigid bar or strap which while allowing rotation prevents the tops of the posts 84 from moving away from each other as the blocks force the electrodes against the link in the welding action. In carrying out our invention a yoke consisting of two horizontal arms 44 and 46 pivoted at the front ends to a tie bar 48 and having journals just back of this bar for receiving the posts 36. The rear ends of the arms are resiliently connected by a rather stiff spring 50. This yoke mechanism constitutes means for permitting the posts 36 to move toward and away from each other a limited amount during the welding operation.

A member 5| fixed to the arm 44 and projecting over the arm 46 carries an adjustable stop 52 for preyenting the arms from spreading apart too far at the final up-set of the joint. A sec-- and member 54 also fixed to the arm 44 carries a second adjustable stop 56 limiting the closing movement of the arms.

These stops 52 and 56 are adjusted in accordance.with the size and quality of the links of the chain being operated on and the adjustment may be changed merely by moving the screws 52 and 56.

The control switch mechanism is mounted on still a third member 60 which is also rigidly secured t the arm 44 as by means of cap screws 6| and which extends over the arm 46. A switch arm 63 depends from the end of the arm 60 with which it has a hinge-like connection 64 so that it can swing toward and away from a second switch arm 65 (Fig. 2) projecting downward from the member 60 on the opposite side of the arm 46. Adjustable contacts 61 and 68, respectively, carried by the switch arms, are urged into contact by a spring 69 but are normally separated when the yoke arms 44 and 46 move apart sufficiently to bring arm 46 into engagement with the set screw ll "carried by the arm 63. Expressed in other words, when the arms 44 and 46 are spread apart as at the beginning of a welding operation the switch contacts are likewise held apart due to the set screw H engaging the arm 45 but as the welding proceeds the arms 44 and 46 gradually move toward each other and permit contacts 6! and 68 to come into quick engagement, thereby closing the control circuit through the clutch operating solenoid 13 as best shown in Figure 2. A part or all of the switch arms 63 and 65 are made of fibre composition or other insulating material.

Due to the fact that the yoke arms 44 and 46 are many times longer than the distance between a pivot 38 and the tie bar 48 and also due to the fact that the set screw H is positioned so close to the hinge 64, the slight relative motion of the posts 36 will be greatly multiplied so that extremely accurate adjustment may be made to open or close the control circuit at a precisely predetermined condition of the link ends. The movement of the posts 36 toward each other is so greatly multiplied that an operator, by observing the movement of the arms 44 and 46 is able to operate the clutch lever 32, if he likes, with the control circuit entirely disconnected thereby to open the work circuit at almost exactly the proper time and without in any way watching the weld. It will be seen therefore that the yoke mechanism just described permits an accurate control of the weld in accordance with the condition of the entire link rather than the temperature, color, or appearance of the weld itself which indicia have been used in the past for guiding the operator in controlling the machine.

Referring to Figure 2, an understanding of the sequence of operations will easily be obtained.

The primary and secondary of the transformer are conventionally indicated at 88 and 8| respectively, the secondary being connected to the electrodes 38 which serve to complete the circuit through the link 40. The main switch 83 is closed by the cam 84 on the shaft and opened by the spring 85 upon the rotation of the cam 84; the shaft i 5 being rotated when the clutch 38 is engaged by operation of the control handle 32 due to the energization of the solenoid 13 which, as already stated, occurs when the contacts 61 and 88 first engage. The cam 84 is so related to the switch 83 that as soon as the clutch 3| is engaged and the shaft ll turns a few degrees the line circuit is opened.

The operation of the machine will now be explained. The electrodes 38 are first adjusted to engage the link 48 with less pressure than used in the standard machine, however with sufficient pressure to prevent burning where they make contactwith the link. It will be assumed that the chain has been advanced by rotation of the shaft II to place an unwelded link 48 in position between the electrodes 38 and the seats 86 and that such rotation of the main shaft l i has turned the face cams I8 to spread the free ends of the arms 28 which action turns the blocks 35 about the pivots 36 and clamps the electrodes and seats 86 against the link with suflicient force to press the ends of the link against each other. This rotation of the shaft II also brings the cam 84 into a position in which the main switch 83 is closed at approximately the same time as the link ends are pressed together so that at this moment the work current begins to flow through the link.- When the link is cold it of course exerts the greatest resistance against the rotation of the blocks 35 toward each other and therefore at this time they exert the greatest force tend ng to separate the pivot posts 36 so that at the moment the current begins to fiow the ends of arms 44 and 46 are farthest apart in which position the contacts 61 and 68 are also most distantly separated. The distance apart of contacts 61 and 68 when regulated for the size of the link and the quality of the material of the link is fixed by the lock nuts 18. current beings to flow there is first a glow at the contact point between the link ends, the inside point then reddens and this spot grows around and toward the front of the link and then arcs appear which also increase until there is a momentary flashing all around the joint. The flashing is believed to be due to the use of a higher current in combination with the increase of resistance as the contacting ends fuse. The increase of resistance is partly due to the flowing away of the hot metal to create what is in effect an air gap by an almost complete pressure drop and is partly due to the increase in temperature of the metal. Immediately following this flashing the electrical resistance of the joint evidently reaches a maximum for the current flow through the back of the link increases sufficiently to heat the back of the link visibly. at which time the bend resistance in the link drops below the pressure on the link exerted by the spring 50 which bends the link and causes the now molten ends to merge into each other. The arms 84 and 46 move toward each other due to the heating and resultant bending of the link which motion brings the contacts 61'and 68 sharply together, therebv energizing the solenoid 13, and thus operatin the clutch 31 causing the rotation of the shaft H which substantially simultaneously opens the The moment the weldingmain circuit 83, and drops the swaging-hammers on the weld.

Still a third action occurs which is the final upset just prior to the swaging blow which upset is caused by the further spreading of the arms 20 due to the action of the swells 88 on the face cams i8. As previously pointed out we not only use a higher temperature than was possible on the standard machine but we also eliminate entirely the second dwell during the increased upset. The usual increase from initial to final upset is about an eighth of an inch on the face cam but we increase the final upset while keeping the size of the initial upset during the swell as in prior practice, the increase of upset from initial to final (without dwell);. lgein g, roughly a third of an inch on the face cani' 20, readily obtained by securing to the cam a' flat strip bevelled at its two ends. The clutch 38 is as usual automatic so that immediately after'the close of the main shaft cycle ending with the closing of the clutch 83 the clutch automatically opens thus permitting the followers 19 to rest against the now stationary initial upset swells 98 of the face cams. It will of course be understood that the trimmer 26 operatesin its usual manner to remove the burrs which in the process just described are very much softer than in ordinary chain and therefore moreeasily cut than would be expected in'high carbon and. alloy steels for which this method was developed as has just been described.

It will be understood that since the control cir-- cuit is dependent for current on the closing of the switch 83 shortly after the contacts 61 and 68 engage, the control circuit is de-energized and that the operating handle 32 is immediately restored to inoperative position by the usual spring 88 whereby the automatic declutching mechanism is permitted to operate to stop the main shaft II at the proper point.

It is well understood in the chain making art that as the links come from theforming machine, although apparently quite uniform, the individual links are in fact sufficiently different inlength to require an appreciably different amount of current and a different amount of time to form the proper weld and it is for this reason that the automatic control should be responsive to the condition of the weld and link as a whole rather than to any predetermined time of current flow or other observable factor such as color or yield of the weld per se. The condition of the link and Weld is a resultant of all these factors. In the process we have just described for any given s'ze of link as delivered by the forming machine, the links are all welded uniformly and are made much more uniform in length than was possible by any prior known method.

In the manually controlled machine not equipped with our improved yoke the operator depended on the time of current flow and/or the color and condition of the weld to guide him n operating the clutch handle 32. Under such conditions the back of a long link would be relatively cold at the time the weld gave every indication of being complete so that the operaor would cut off the welding current-and leave the link under a strain which u on cooling would cause cracks at the we'd which cracks open u when the link is bent 45 to about an axis through the weld. On the other hand a short" link would get too hot at the weld with the same result that cracks would form. It is also obvious that different operators would have different times of reaction so that the welding current to the operator but the cause lay in the prior machines which were set to operate for a certain size link and had no provision, such as our yoke, for operating uniformly on'links which varied in length over an appreciable range for any given size delivered bythe forming machine. In the process we have-described the chains are of uniform quality and the links are of uniform length regardless of whether made by the same or different operators. process we have reduced to a minimum those factors which tend to produce poor or non-uniformchains What we claim is:

l...In; a-chain welding machine having a'pair of electrode-carrying blocks mounted to turn about apair of substantially parallel axes, means for turning said blocks through a limited angle about another pair of axes approximately normal to the first pair. r

'2. In a chain'welding machine having a pair of electrode blocks pivoted on substantially par-' In other words by our new.

BESTAVAILABLE COPY V 6.. In amachinezfor welding objects-each'im' cluding a bar and two pieces vroughly parallel thereto, pressure exerting means for moving the two pieces into abutting. relation, means ior holdi s said bar .in rig d parallel relation with'said pieces wherebypressure forcing .said pieces togetheris'resisted in part by saidzbar, means for passingwelding current through said pieces and through-saldbar wherebysaid bar is heated to '01 the first pair of axes.-. i

a. In a chain welding machine for wvelding high carbon or alloy steel linksiand having a. pair of electrode jaws with plvot postsirising above the jaws, means for equalizing the imperfections in the weld of a chain to avoid weld "cracks,

which consists in-resiliently holding togetherthe .topsor the Jaw pivots,' means.-for1increasing :the

- welding temperature considerably :above that allel-axes. each of said blocks having a link seat consisting in part of a recessed electrode, said seats being opposed in spaced relation to receivev the link of a chain andarranged with respect to said axes to approach or separate Irom each other when said blocks rotate about the axes, each of said blocks having a post rising therelimited arcs about substantially vertical "axes,

commonly usedin welding chains; and means'responsive to the heating of the;entire link to red heat for interrupting flow of welding current;

of electrode blocks -mounted:for movement in each of said blocks having a linkseat, said seats from arranged coaxially of the blocks, means for moving'the tops of said posts with respect to each other to vary the distance between said link seats.

3. In a chain welding machine having a pair of electrode blocks loosely pivoted to turn about substantially vertical axes and means for moving said blocks through a limited angle in said lo'ose pivots about substantially horizontal axes, means for passing a welding current through a link held between said electrode blocks and means for controlling said current in response to the movement of the blocks about said horizontal axes.

being in spaced opposed relation to receivesuccessively the links of a chain and arranged with respect to said axes to approach or retreat from each other when-said blocks movein said arcs.

an upright post rigidly. connected to and Dositionedcoaidally-oreach block, means for yieldingly'urging'the topszot said posts towardeach other to additionally vary the distance betweenthe link seats and means for opp sitel moving the blockson said axes. I

4. In a chain welding machine having a pair of pivoted electrode blocks, a yoke comprising a tie bar, a pair of arms pivoted to said tie bar in spaced relation, said arms being connected to the b10cks,'spring means for urging said arms toward each other about their respective tie-bar pivots thereby to move the blocks with respect to each other, means for limiting the closing movement of said arms and switch means controlled by said movement for controlling welding current to the machine.

5. In an electric chain welding machine having a welding circuit chain advancing means. burr removing means, a chain holding and welding means operated from a common shalt, a clutch for connecting said shaft to a source of power, an electro-magnetic device for engaging said clutch: said holding and welding device con- 10. Ina chain welding machine havinga pair of opposed electrode carryingblocks mounted for limited and relatively .opposite'rctation about a I pair of substantially .parallel taxes. said blocks having opposed link seats for cooperatively receiving and holding a chain link,ameans for producing said limited opposite rotation of the blocks to vary the distance between said link seats and adjustable spring means tending to produce limited and relatively opposite'rotation of the blocks about a different pair of axes lying in a plane at a substantial angle to the first pair of axes whereby to control the efiective pressure of the blocks on links held in the link seats.

11. In a chain welding machine of the type having a plurality of electrode carrying blocks looselymounted in the table or base, with vertical posts rising from said blocks which are oscillated by means 01' arms engaging pressure producingcams; the combination of a yoke connecting the post tops in place of the usual brace. means urging the. yoke arms to move the post tops together during the welding operation and means, inoperative when the chain link is cold, to control the pressure on the joint when the weld is substantially at the welding heat, whereby a better weld is secured than if the post tops were rigidly held, and unwelded links of slightly different diameter, width, or length are made into uniform welded links.

12. In a chain welding machine of the type employing a pair oi posts andelectrode carrying jaw levers pivoted on said posts: apair of onedwell cams operating said levers and having a.

of claim 1 in which-said'means clutch for starting the cams and for completing the electric circuit, and means responsive to the lowering of the resistance to bending of the link for shutting off the welding current, whereby to increase the uniformity in gage length of the finished chain because of the greater amount of current given to a long link and the less amount of current given a short link.

GUSTAVE K. BLUM. ARTHUR E. PETERS. 

